In many industries and, in particular, in the automotive industry, there is a need for connecting together various engine parts and equipment contained in the engine compartment of the vehicle. For example, plumbing lines are necessary between various parts of the air conditioning system, such as the condenser, compressor and evaporator. These plumbing lines are typically provided by flexible tubing; and it is desirable to be able to make the connection without extensive use of equipment or manipulation and/or adaption of the tube parts. It is also desirable to have the connection of the tubes made in such a way that they can be disconnected for repair or replacement of the associated equipment or the tubes themselves.
Besides the need for making a connection which is initially fluid-tight, consideration must be given to constructing the coupling so that the tube connection remains fluid-tight over extended use of the vehicle. With quick-connect couplings, this has generally been found to be difficult to attain. The very purpose of the quick-connect coupling is to permit an easy and quick connection and disconnection of the tube parts without the need for attachment of auxiliary clamping structure or tools. This is generally at odds with the need for assuring that the connection remains fluid-tight over extended use.
With automotive equipment, tube couplings or connections are continuously subjected to vibration and flexing during use of the vehicle. A typical prior art quick-connect coupling is disclosed in U.S. Pat. No. 4,055,359. Couplings of this type are presently in wide use in the automotive industry. It has been found, however, that even with a proper initial coupling of the tube parts, this type of structure does have a tendency, over time, to become disconnected due to vibration and flexing, particularly when the system is pressurized. Part of the reason for this malfunctioning is believed to be caused due to the manner in which the initial connection of the coupling is made. As disclosed in the '359 patent, the connection is effected by a simple axial movement of the tube ends together. This movement causes a spring member of the coupling to expand and position itself tightly around the coupled ends of the tubes. The spring member is, however, not restrained against expanding once the tube parts are coupled together. It is therefore free to move to an uncoupling position whenever the forces acting on the coupling, such as vibration and flexing, act on the spring in an uncoupling direction.